The invention relates to a starter for an internal combustion engine. By way of example, one such starter is described in the Kraftfahrtechnischen Taschenbuch (Motor vehicle manual) produced by Bosch, 25th edition, page 986, in the form of a pre-engaged Bendix starter, which is operated via a so-called pull-in relay. This relay carries out the pulling-in functions, that is to say engaging the pinion of the starter motor in the toothed rim on an internal combustion engine, and switching the main current of the starter motor. In this case, a distinction can be drawn between two possible processes when the pinion engages in the toothed rim: in about 20%-30% of switching operations, one tooth of the pinion engages in a gap in the toothed rim, while, in approximately 70%-80% of the switching operations, one tooth of the pinion strikes a tooth on the toothed rim during engagement, and the engagement process must be assisted by an engagement spring. This known starter design admittedly requires only a single relay and can therefore be produced at relatively low cost, but on the other hand it results in very difficult working conditions for the switching process for the high motor current on the switching contact which connects the motor windings to the voltage source. Particularly in the case of partially discharged batteries and as the mechanical wear on the engagement parts increases, the dynamic response when switching on the main starter current can decrease to such an extent that the contacts are welded by arcs which occur during the switching process. On the other hand, if the pinion engages directly in the engine toothed rim, the dynamic response of the switching process and the contact wear resulting from it may possibly be high, depending on the design of the starter, when starting from an initial tooth-in-gap position.
In order to improve the switching-on process, particularly in the case of high-power starters, it is also known from the abovementioned reference for the motor current to be switched on in two stages in so-called pre-engaged starters wherein, in a first stage, the pinion of the starter is moved against the toothed rim of the engine, and the armature of the starter motor is at the same time fed with a reduced current, as a result of which the armature and, with it, the pinion, rotate during the engagement process, thus simplifying the engagement process. The engagement mechanism is in this case provided with a ratchet which closes a further switching contact of the relay and, via this, the main current circuit of the motor, only at the end of the engagement process of the pinion. This allows the engagement process and the switching of the main current of the motor to be carried out in two separate processes, but the design of the pull-in relay is more complex and more susceptible to defects, from the mechanical and electrical points of view.